Send to

Choose Destination
See comment in PubMed Commons below
Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):565-70. Epub 2005 Jan 7.

The Birc6 (Bruce) gene regulates p53 and the mitochondrial pathway of apoptosis and is essential for mouse embryonic development.

Author information

  • 1Stowers Institute for Medical Research, Kansas City, MO 64110, USA.


Baculoviral inhibitor of apoptosis repeat-containing (Birc)6 gene/BIRC6 (Bruce/APOLLON) encodes an inhibitor of apoptosis and a chimeric E2/E3 ubiquitin ligase in mammals. The physiological role of Bruce in antiapoptosis is unknown. Here, we show that deletion of the C-terminal half of Bruce, including the UBC domain, causes activation of caspases and apoptosis in the placenta and yolk sac, leading to embryonic lethality. This apoptosis is associated with up-regulation and nuclear localization of the tumor suppressor p53 and activation of mitochondrial apoptosis, which includes up-regulation of Bax, Bak, and Pidd, translocation of Bax and caspase-2 onto mitochondria, release of cytochrome c and apoptosis-inducing factor, and activation of caspase-9 and caspase-3. Mutant mouse embryonic fibroblasts are sensitive to multiple mitochondrial death stimuli but resistant to TNF. In addition, eliminating p53 by RNA interference rescues cell viability induced by Bruce ablation in human cell line H460. This viability preservation results from reduced expression of proapoptotic factors Bax, Bak, and Pidd and from prevention of activation of caspase-2, -9, and -3. The amount of second mitochondrial-derived activator of caspase and Omi does not change. We conclude that p53 is a downstream effector of Bruce, and, in response to loss of Bruce function, p53 activates Pidd/caspase-2 and Bax/Bak, leading to mitochondrial apoptosis.

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Support Center